Childhood obesity is a global epidemic with costly comorbidities. In the US, the rate of obesity has tripled over the past 40 years. Diet, physical activity, and genetics do not explain all of the variability in weight, and moreover can be difficut to modify. Identifying environmental triggers and feasible public health interventions is therefore a policy imperative. Prior data from this team has suggested an association of prenatal exposure to air pollution with maternal hyperglycemia and reduced fetal growth. Paradoxically we have also demonstrated an association between greater prenatal traffic-related pollution and excess infant weight gain after birth, leading to higher risk for obesity in infancy. With the guidance of my mentoring team, during this 5 year K23 career development award, the Candidate will leverage data from two prospective longitudinal cohorts of mothers and children (Project Viva, n=2,128 and the New Hampshire Birth Cohort Study (NHBCS), n=1,500) to extend this prior work through three inter-related projects. The Principal Investigator will: (1) examine prenatal exposure to ambient air pollution as a risk factor for rapid weight trajectories throughout childhood and central fat accrual in mid-childhood. (2) consider the relationship of prenatal air pollution exposure with obesity-associated hormonal biomarkers, including leptin, adiponectin, and insulin resistance in childhood. (3) characterize exposures and habits related to indoor sources of air pollution in rural New England and estimate the extent to which indoor wood burning during pregnancy is associated with maternal hyperglycemia, fetal growth, and offspring weight gain in early childhood. The training plan proposed will build upon my clinical training in pediatric endocrinology and basic knowledge of biostatistics and epidemiology to provide formal training in (1) environmental exposure assessment, (2) statistical techniques necessary to analyze complex exposure-response relationships, and (3) the practical skills necessary to lead a research team. The Candidate will leverage the wealth of resources available at Boston Children's Hospital, the Department of Population Medicine (Harvard Medical School and Harvard Pilgrim Health Care), the Harvard School of Public Health, and the Dartmouth Children's Environmental Health and Disease Prevention Research Center to conduct the proposed analyses. These studies and training will lay the necessary scientific framework to launch her career as an independent physician researcher studying the impact of environmental toxicants on children's health, with a focus on obesity and insulin resistance.